The present invention relates generally to gas turbine engines, and, more specifically, to seals therein.
In a gas turbine engine, air is pressurized in a compressor, mixed with fuel in a combustor, and ignited for generating hot combustion gases which flow downstream through several turbine stages which extract energy therefrom. The pressurized air surrounds the combustor and is used for cooling the liners thereof. The pressurized air is also used to cool other components of the engine as well.
Since the engine is formed of stator components which are suitably joined together, various types of static seals must be provided therebetween to reduce or prevent undesirable leakage of either the pressurized air or the hot combustion gases. The seals have different cross-sectional configurations for specifically sealing different components. For example, the seals may have a W-shape cross-section, or an E-shape, or simply circular cross-sections depending upon the specific application requiring sealing.
Some seals are full rings, or they may be circumferentially split at one location to eliminate undesirable hoop stress therein. Another type of seal is in the form of a flat, straight leaf seal disposed in complementary slots between adjoining components.
The seals are subject to various differential thermal movement between the adjoining components including differential radial movement, differential axial movement, or both. Relative radial and axial deflections are common between the aft end of the combustor outer liner and the forward end of the outer band of the adjoining high pressure turbine nozzle. Under the high temperature of the combustion gases produced in the combustor, the outer liner can expand radially outwardly significantly more than the radially outer expansion of the outer band. And, the axial gap between the two components may also grow substantially large during operation.
Accordingly, one form of leaf seal is used at this location in which a radial leaf seal engages a complementary radial slot for accommodating differential radial movement, and an axial leaf seal engages a complementary axial slot for accommodating differential axial movement. However, since the leaf seals are straight in cross-section and can distort during operation, their sealing ability can be compromised. Furthermore, some leaf seals are provided in segments, which interrupt the sealing capability between the segments.
Accordingly, it is desired to provide an improved ring seal for sealing high excursion differential radial and axial movement between gas turbine engine stator components.